Method for manufacturing insulated gate field effect transistor

ABSTRACT

An insulated gate field effect transistor with (a) a base having source/drain regions, a channel forming region, a gate insulating film formed on the channel forming region, an insulating layer covering the source/drain regions, and a gate electrode formation opening provided in a partial portion of the insulating layer above the channel forming region; (b) a gate electrode formed by burying a conducive material layer in the gate electrode formation opening; (c) a first interlayer insulating layer formed on the insulating layer and the gate electrode and containing no oxygen atom as a constituent element; and (d) a second interlayer insulating layer on the first interlayer insulating layer.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/982,095 filed May 17, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/560,123 filed Dec. 4, 2014, now U.S. Pat. No.10,014,384 issued Jul. 3, 2018, which is a continuation of U.S. patentapplication Ser. No. 13/916,002 filed on Jun. 12, 2013 now abandoned,which is a division of U.S. patent application Ser. No. 12/031,013 filedFeb. 14, 2008, now U.S. Pat. No. 8,486,789 issued on Jul. 16, 2013 theentireties of all which are incorporated herein by reference to theextent permitted by law. The present invention claims priority to andcontains subject matter related to Japanese Patent Application JP2007-035007 filed in the Japan Patent Office on Feb. 15, 2007, theentire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a method for manufacturing an insulatedgate field effect transistor.

2. Description of the Related Art

Currently, miniaturization of transistors is being advanced based on theso-called scaling rule, and thereby enhancement in the integrationdegree and the operating speed of semiconductor devices is beingpromoted. For miniaturization of an insulated gate field effecttransistor (metal insulator semiconductor FET (MISFET)), it is demandedto suppress the influence of the so-called short-channel effect. As longas a gate electrode is composed of a semiconductor material, it isdifficult to effectively suppress the depletion of the gate electrode,which is one of factors in the short-channel effect. To address thisproblem, there has been proposed a scheme in which a gate electrode isformed by using a conductive material such as a metal or metal compound.As a method for forming a gate electrode by using a conductive material,there has been proposed a method in which e.g. a metal film is depositedinstead of a polycrystalline silicon film and this metal film ispatterned to thereby form a gate electrode similarly to related-artmethods. Furthermore, there has also been proposed a method in which agate electrode is formed by a so-called damascene process of burying aconductive material in a gate electrode formation opening (refer toe.g., Atsushi Yagishita et al., “High Performance Metal Gate MOSFETsFabricated by CMP for 0.1 μm Regime,” International Electron DevicesMeeting 1998 Technical Digest p.p. 785-788 (1998) and Japanese PatentLaid-Open No. 2005-303256). In the method of forming a gate electrode bya damascene process, a gate insulating film composed of e.g. aninsulating material (e.g., hafnium oxide) having a relative dielectricconstant higher than that of silicon oxide is formed in a gate electrodeformation opening arising from removal of a dummy gate electrode, andthen a gate electrode is formed. This method can enhance characteristicsof the insulated gate field effect transistor.

The outline of a method for forming a gate electrode by a related-artdamascene process will be described below with reference to FIGS. 1C,1D, 1E, 1F, 5A, and 5B, which are schematic partial end views of asilicon semiconductor substrate and so on.

[Step-10]

Initially, a base 10 is prepared that includes source/drain regions 13,a channel forming region 12, a gate insulating film 30 that is formed onthe channel forming region 12 and composed of hafnium oxide, aninsulating layer 21 that is composed of SiO₂ and covers the source/drainregions 13, and a gate electrode formation opening 22 that is providedin a partial portion of the insulating layer 21 above the channelforming region 12 (see FIGS. 1C and 1D).

A method for manufacturing the base 10 will be described in detail laterin the explanation of a first embodiment of the present invention. Inthe drawings, reference numeral 11 denotes a silicon semiconductorsubstrate. Reference numeral 13A denotes a silicide layer formed inupper part of the source/drain regions 13. Reference numeral 17 denotesa side wall film.

[Step-20]

After the preparation of the base 10, a work function control layer 31composed of a metal material (hafnium silicide) for defining the workfunction of the gate electrode and a barrier layer (not shown) composedof TiN are sequentially formed across the entire surface (see FIG. 1E).Thereafter, a conductive material layer 32 composed of tungsten isformed across the entire surface based on so-called blanket tungstenCVD. Subsequently, planarization treatment based on CMP is carried outto remove the conductive material layer 32, the barrier layer, the workfunction control layer 31, and the gate insulating film 30 over theinsulating layer 21 and the side wall film 17. In this manner, a gateelectrode 23 can be obtained (see FIG. 1F). The gate electrode 23 isformed above the channel forming region 12 with the intermediary of thegate insulating film 30 therebetween and is formed of the work functioncontrol layer 31, the barrier layer (not shown), and the conductivematerial layer 32.

[Step-30]

Subsequently, an interlayer insulating layer 142 composed of SiO₂ isformed by e.g. high-density plasma CVD across the entire surface (seeFIG. 5A).

[Step-40]

Subsequently, based on photolithography and dry etching, contact plugformation openings 43A and 43B are formed in partial portions of theinterlayer insulating layer 142 above the gate electrode 23 and abovethe source/drain regions 13. Thereafter, a second barrier layer (notshown) composed of Ti (lower layer)/TiN (upper layer) is formed acrossthe entire surface and then a tungsten layer is formed across the entiresurface based on blanket tungsten CVD. Subsequently, planarizationtreatment based on CMP is carried out, so that contact plugs 44A and 44Bcan be formed in the contact plug formation openings 43A and 43B (seeFIG. 5B).

SUMMARY OF THE INVENTION

In the case of the insulated gate field effect transistor obtained bysuch a manufacturing method, the interlayer insulating layer 142composed of SiO₂ is formed by CVD across the entire surface in [Step-30](see FIG. 5A). Typically, in the composition of the source gas used inthe CVD, oxygen atoms or oxygen molecules are contained. Therefore, inthe formation of the interlayer insulating layer 142 composed of SiO₂,the oxygen atoms or oxygen molecules in the atmosphere pass through theconductive material layer 32, the barrier layer, the work functioncontrol layer 31, and the gate insulating film 30, and reach a partialportion of the silicon semiconductor substrate 11 facing the gateelectrode 23, so that this partial portion of the silicon semiconductorsubstrate 11 is oxidized. In FIGS. 5A and 5B, this oxidized partialportion of the silicon semiconductor substrate 11 is indicated byreference numeral 30A.

The occurrence of such a phenomenon is eventually equivalent to increasein the film thickness of the gate insulating film 30, which results inthe deterioration of characteristics of the insulated gate field effecttransistor, such as the lowering of the gate capacitance.

There is a need for the present invention to provide a method formanufacturing an insulated gate field effect transistor, free fromoxidation of a partial portion of a base facing a gate electrode at thetime of formation of an interlayer insulating layer above the gateelectrode.

A method for manufacturing an insulated gate field effect transistoraccording to a first mode of the present invention (hereinafter,abbreviated as the manufacturing method according to the first mode ofthe present invention) includes the steps of (a) preparing a base thatincludes source/drain regions, a channel forming region, a gateinsulating film formed on the channel forming region, an insulatinglayer covering the source/drain regions, and a gate electrode formationopening provided in a partial portion of the insulating layer above thechannel forming region, (b) forming a gate electrode by burying aconductive material layer in the gate electrode formation opening, (c)removing the insulating layer, and (d) depositing a first interlayerinsulating layer and a second interlayer insulating layer sequentiallyacross the entire surface. In the step (d), the first interlayerinsulating layer is deposited in a deposition atmosphere containing nooxygen atom.

In the manufacturing method according to the first mode of the presentinvention, the first interlayer insulating layer and the secondinterlayer insulating layer are sequentially deposited, specifically, onthe gate electrode and the source/drain regions across the entiresurface.

A method for manufacturing an insulated gate field effect transistoraccording to a second mode of the present invention (hereinafter,abbreviated as the manufacturing method according to the second mode ofthe present invention) includes the steps of (a) preparing a base thatincludes source/drain regions, a channel forming region, a gateinsulating film formed on the channel forming region, an insulatinglayer covering the source/drain regions, and a gate electrode formationopening provided in a partial portion of the insulating layer above thechannel forming region, (b) forming a gate electrode by burying aconductive material layer in the gate electrode formation opening, and(c) depositing a first interlayer insulating layer and a secondinterlayer insulating layer sequentially across the entire surface. Inthe step (c), the first interlayer insulating layer is deposited in adeposition atmosphere containing no oxygen atom.

In the manufacturing method according to the second mode of the presentinvention, the first interlayer insulating layer and the secondinterlayer insulating layer are sequentially deposited, specifically, onthe gate electrode and the insulating layer across the entire surface.

In the step (d) of the manufacturing method according to the first modeof the present invention, and in the step (c) of the manufacturingmethod according to the second mode of the present invention, the secondinterlayer insulating layer can be deposited in a deposition atmospherecontaining an oxygen atom. In this case, it is desirable that the firstinterlayer insulating layer be composed of a silicon nitride (SiN) or asilicon carbide (SiC) and the second interlayer insulating layer becomposed of a silicon oxide (SiO_(x)).

In the manufacturing methods including the above-described preferredconfiguration according to the first and second modes of the presentinvention, a configuration can also be employed in which the insulatinglayer is formed of the lower insulating layer and the upper insulatinglayer formed on this lower insulating layer and the lower insulatinglayer covers at least the source/drain regions. In the manufacturingmethod according to the first mode of the present invention, it ispreferable that the upper insulating layer be removed and the lowerinsulating layer be left in the step (c). Furthermore, in these cases,it is desirable that the lower insulating layer be composed of the samematerial as that of the first interlayer insulating layer and the upperinsulating layer be composed of the same material as that of the secondinterlayer insulating layer, but this configuration imposes nolimitation. Specifically, it is desirable that the first interlayerinsulating layer and the lower insulating layer be composed of a siliconnitride (SiN) or a silicon carbide (SiC) and the second interlayerinsulating layer and the upper insulating layer be composed of a siliconoxide (SiO_(x)). If the insulating layer is formed of the lowerinsulating layer and the upper insulating layer, in the manufacturingmethod according to the first mode of the present invention, the firstinterlayer insulating layer and the second interlayer insulating layerare sequentially deposited, specifically, on the gate electrode and thelower insulating layer across the entire surface. On the other hand, inthe manufacturing method according to the second mode of the presentinvention, the first interlayer insulating layer and the secondinterlayer insulating layer are sequentially deposited, specifically, onthe gate electrode and the upper insulating layer across the entiresurface.

It is preferable for the base to further include a side wall film thatdefines the side face of the gate electrode formation opening.Furthermore, it is desirable that the material of at least one partialportion of the side wall film be different from the material of theinsulating layer (or the upper insulating layer). Specifically, e.g. SiNcan be used as the material of the partial portion of the side wall filmin contact with the side surface of the gate electrode. If theinsulating layer is formed of the lower insulating layer and the upperinsulating layer, the lower insulating layer may extend on the sidesurface of the side wall film. In the present specification, aninsulating layer covering source/drain regions and a side wall film areoften referred to collectively as an insulating layer. If the base hasthe side wall film, in the manufacturing method according to the firstmode of the present invention, the first interlayer insulating layer andthe second interlayer insulating layer are sequentially deposited,specifically, on the gate electrode, the side wall film, and thesource/drain regions, or on the gate electrode, the side wall film, andthe lower insulating layer, across the entire surface. On the otherhand, in the manufacturing method according to the second mode of thepresent invention, the first interlayer insulating layer and the secondinterlayer insulating layer are sequentially deposited, specifically, onthe gate electrode, the side wall film, and the insulating layer, or onthe gate electrode, the side wall film, and the upper insulating layer,across the entire surface.

In the step (d) of the manufacturing method including theabove-described preferred configuration according to the first mode ofthe present invention, and in the step (c) of the manufacturing methodincluding the above-described preferred configuration according to thesecond mode of the present invention, it is preferable that the firstinterlayer insulating layer be deposited (formed) based on chemicalvapor deposition (any of various kinds of CVD, such as plasma CVD,high-density plasma CVD, and atmospheric-pressure CVD, including atomiclayer deposition (ALD)) in which a source gas with a compositioncontaining neither an oxygen atom nor an oxygen molecule is used. On theother hand, it is preferable that the second interlayer insulating layerbe deposited (formed) based on any of various kinds of CVD in which asource gas with a composition containing an oxygen atom or an oxygenmolecule is used. However, embodiments of the present invention are notlimited thereto, but the first interlayer insulating layer and thesecond interlayer insulating layer may be deposited (formed) by any ofphysical vapor deposition (PVD) methods such as sputtering, evaporationtypified by electron-beam evaporation and hot-filament evaporation, ionplating, and laser ablation. In this case, it is preferable that thefirst interlayer insulating layer be deposited (formed) based on PVD inan atmosphere containing neither an oxygen atom nor an oxygen moleculeand the second interlayer insulating layer be deposited (formed) basedon PVD in an atmosphere containing an oxygen atom or an oxygen molecule.

In the manufacturing methods including the above-described preferredconfiguration according to the first and second modes of the presentinvention (hereinafter, these methods will be often referred to simplyas the manufacturing methods of the present invention collectively), thewhole of the gate electrode may be formed of the conductive materiallayer. Alternatively, the bottom and side portions of the gate electrodemay be formed of a work function control layer for defining the workfunction of the gate electrode, and the center portion (remainingportion) surrounded by the bottom and side portions may be formed of theconductive material layer. In the latter case, it is desirable that theelectric resistivity of the conductive material of the conductivematerial layer be lower than that of the conductive material of the workfunction control layer. In the former form, the forming step for thegate electrode can be simplified. In the latter form, the electricresistance of the gate electrode can be lowered. In addition, furtheranother conductive material layer may be formed between the center andbottom portions of the gate electrode and between the center and sideportions of the gate electrode. That is, the gate electrode may beformed by stacking three or more conductive material layers. As theconductive materials of the conductive material layer and the workfunction control layer, a conductive material is properly selected thathas a favorable work function in terms of the relationship with thechannel forming region of the re-channel or p-channel insulated gatefield effect transistor.

As the conductive materials (metal materials) of the conductive materiallayer and the work function control layer, any of the followingmaterials can be used: metals such as tungsten (W), hafnium (Hf),tantalum (Ta), titanium (Ti), molybdenum (Mo), ruthenium (Ru), nickel(Ni), and platinum (Pt) (including alloys of any of these metals);compounds of any of these metals such as nitrides; and compounds betweena metal and a semiconductor material such as metal silicides. As theconductive material of the work function control layer, a material isproperly selected that has a favorable work function in terms of therelationship with the channel forming region. For example, when thechannel forming region is an n-type, a conductive material (metalmaterial) containing hafnium (Hf), tantalum (Ta), or the like can beselected. When the channel forming region is a p-type, a conductivematerial (metal material) containing titanium (Ti), molybdenum (Mo),ruthenium (Ru), nickel (Ni), platinum (Pt), or the like can be selected.However, the material is not limited thereto. When the conductivematerial layer is formed by using a silicide, the work function of thegate electrode of the n-channel insulated gate field effect transistorand the p-channel insulated gate field effect transistor can beoptimized by controlling the kind and amount of an impurity contained inthe silicide, or by ion-implanting e.g. aluminum ions in the silicide.The gate electrode can be formed by a known damascene process.Specifically, in the damascene process, the conductive material layer isburied in the gate electrode formation opening by carrying out any ofthe following deposition methods alone or in arbitrary combination:various kinds of PVD such as evaporation typified by electron-beamevaporation and hot-filament evaporation, sputtering, ion plating, andlaser ablation; various kinds of CVD including ALD and MOCVD; andplating such as electrolytic plating and electroless plating.Subsequently, planarization treatment is carried out by chemicalmechanical polishing (CMP), etch-back, or the like.

The removal of the insulating layer is carried out based on a methodsuitable for the material of the insulating layer. Examples of themethod include dry etching and wet etching with use of a proper etchant.

In the manufacturing methods of the present invention, the gateinsulating film may be formed after the gate electrode formation openingis formed in the insulating layer. Alternatively, the insulating layerand the gate electrode formation opening may be formed after the gateinsulating film is formed. In the latter case, the gate electrodeformation opening should be formed in such a way that the gateinsulating film is left at the bottom of the opening. Examples of thematerial of the gate insulating film include, in addition to SiO₂-basedmaterials and SiN-based materials, which have been generally used inrelated arts, so-called high relative dielectric constant materials ofwhich relative dielectric constant k (=ε/ε₀) is substantially 4.0 orhigher. Examples of the high relative dielectric constant materialinclude zirconium oxide (ZrO₂), hafnium oxide (HfO₂), aluminum oxide (A1₂O₃), yttrium oxide (Y₂O₃), and lanthanum oxide (La₂O). In addition, theexamples further include metal silicates such as HfSiO, ZrSiO, AlSiO,and LaSiO. The gate insulating film may be formed by using either onekind of material or plural kinds of materials. Furthermore, the gateinsulating film may be formed as either a single film (encompassing acomposite film composed of plural materials) or multilayer film. Thegate insulating film of the n-channel insulated gate field effecttransistor and that of the p-channel insulated gate field effecttransistor can be formed by using either the same material or materialsdifferent from each other. The gate insulating film can be formed by awell-known method. In particular, CVD encompassing ALD and metal organicchemical vapor deposition (MOCVD) can be used as a method for formingthe gate insulating film composed of the above-described high relativedielectric constant material.

In the manufacturing methods of the present invention, examples of thematerial of the insulating layer include, besides the above-describedSiO₂ and SiN, SiON, SiOF, SiC, and low dielectric constant insulatingmaterials of which dielectric constant k (=ε/ε₀) is e.g. 3.5 or lower,such as organic SOG, polyimide-based resin, and fluorine-based resin(e.g., fluorocarbon, amorphous tetrafluoroethylene, polyarylether,arylether fluoride, polyimide fluoride, parylene, benzocyclobutene,amorphous carbon, cycloperfluorocarbon polymer, and fluorofullerene). Itis also possible for the insulating layer to be formed by using amultilayer structure formed of any of these materials.

In partial portions of the interlayer insulating layers located abovethe channel forming region and the source/drain regions, contact plugsconnected to the gate electrode and the source/drain regions may beformed. Examples of the material of the contact plugs includepolycrystalline silicon doped with an impurity and refractory metalmaterials such as tungsten (W). The contact plugs can be formed byproviding contact plug formation openings in the interlayer insulatinglayers by dry etching such as RIE and then filling the contact plugformation openings with the above-described material by a known method.Specifically, for example, the contact plugs can be formed by buryingtungsten in the contact plug formation openings by blanket tungsten CVDand then removing the excess tungsten layer on the interlayer insulatinglayer. A form is also available in which a Ti layer and a TiN layer asan adhesion layer are formed inside the contact plug formation openingsand then tungsten is buried in the contact plug formation openings byblanket tungsten CVD.

It is desirable that the top surfaces of the source/drain regions beformed of a silicide layer for reduced contact resistance.

As the base that is used in the manufacturing methods of the presentinvention and includes the source/drain regions, the channel formingregion, and so on, besides a semiconductor substrate such as a siliconsemiconductor substrate, a support member of which surface has asemiconductor layer (e.g., a glass substrate, quartz substrate, siliconsemiconductor substrate of which surface has an insulating materiallayer, plastic substrate, or plastic film) can be used. The insulatedgate field effect transistor is formed in e.g. a well region or the likein a semiconductor substrate or semiconductor layer. A so-called elementisolation region having e.g. a trench structure may be formed betweenthe insulated gate field effect transistors. The element isolationregion may have a LOCOS structure, or may be based on the combination ofa trench structure and a LOCOS structure. More alternatively, the basehaving an SOI structure arising from SIMOX or substrate bonding may beused. A known method can be used as a method for preparing the base thatincludes the source/drain regions, the channel forming region, the gateinsulating film formed on the channel forming region, the insulatinglayer covering the source/drain regions, and the gate electrodeformation opening provided in a partial portion of the insulating layerabove the channel forming region, i.e., a method for fabricating such abase.

The term “channel forming region” indicates not only a region in whichthe channel is actually formed but also a region in which the channelwill be possibly formed. For example, partial portions of asemiconductor layer and a semiconductor substrate located to face thegate electrode correspond to the “channel forming region.” Furthermore,the “gate electrode” encompasses not only the electrode portion facingthe “channel forming region” but also a lead-out electrode part as anextension from this electrode portion. An insulated gate field effecttransistor manufactured by the manufacturing methods of the presentinvention may be e.g. a CMOS semiconductor device formed of an n-channelMOS and a p-channel MOS, instead of an n-channel MISFET and a p-channelMISFET. Alternatively, it may be a BiCMOS semiconductor device includinga bipolar transistor in addition to an n-channel MOS and a p-channelMOS.

In the manufacturing methods of the present invention, the firstinterlayer insulating layer and the second interlayer insulating layerare sequentially deposited across the entire surface after the gateelectrode is formed. In this deposition, the first interlayer insulatinglayer is deposited in a deposition atmosphere containing no oxygen atom.This feature can surely prevent the occurrence of a phenomenon ofoxidation of a partial portion of the base (e.g., a siliconsemiconductor substrate) facing the gate electrode, and thus can surelyavoid the occurrence of a problem of the deterioration ofcharacteristics of the insulated gate field effect transistor, such asthe lowering of the gate capacitance.

In the manufacturing method according to the first mode of the presentinvention, the configuration of the components above the gate electrode(the configuration of the interlayer insulating layers) can be madesubstantially the same as that of the components above the source/drainregions (the configuration of the insulating layer+the interlayerinsulating layers). Thus, the contact plug formation openings can beeasily formed for the provision of the contact plugs for the gateelectrode and the source/drain regions.

Furthermore, in the manufacturing methods of the present invention, ifthe insulating layer is formed of the lower insulating layer and theupper insulating layer, it is possible to make the lower insulatinglayer function as a liner layer, and thus stress can be applied to thechannel forming region. As a result, the driving ability of theinsulated gate field effect transistor can be enhanced. Moreover, in themanufacturing method according to the first mode of the presentinvention, the upper insulating layer is removed whereas the lowerinsulating layer is left. Therefore, in this insulating layer removal,no damage occurs to the source/drain regions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1I are schematic partial end views of a semiconductorsubstrate and so on, for explaining a method for manufacturing aninsulated gate field effect transistor according to a first embodimentof the present invention;

FIGS. 2A to 2I are schematic partial end views of a semiconductorsubstrate and so on, for explaining a method for manufacturing aninsulated gate field effect transistor according to a second embodimentof the present invention;

FIGS. 3A and 3B are schematic partial end views of a semiconductorsubstrate and so on, for explaining a method for manufacturing aninsulated gate field effect transistor according to a third embodimentof the present invention;

FIGS. 4A and 4B are schematic partial end views of a semiconductorsubstrate and so on, for explaining a method for manufacturing aninsulated gate field effect transistor according to a fourth embodimentof the present invention; and

FIGS. 5A and 5B are schematic partial end views of a semiconductorsubstrate and so on, for explaining a related-art method formanufacturing an insulated gate field effect transistor and a problem ofthe method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to the accompanying drawings.

First Embodiment

A first embodiment of the present invention relates to a method formanufacturing an insulated gate field effect transistor according to thefirst mode of the present invention.

As shown in the schematic partial end view of FIG. 1I, an insulated gatefield effect transistor obtained by the method for manufacturing aninsulated gate field effect transistor according to the first embodimentincludes (A) source/drain regions 13 and a channel forming region 12,(B) a gate electrode 23 formed above the channel forming region 12, and(C) a gate insulating film 30. In the first embodiment, and in second tofourth embodiments of the present invention, which will be describedlater, an n-channel insulated gate field effect transistor is formed.

The gate insulating film 30 is composed of hafnium oxide. The gateelectrode 23 is formed of a work function control layer 31 and aconductive material layer 32. The work function control layer 31 iscomposed of a conductive material (metal material) for defining the workfunction of the gate electrode 23, and specifically composed of hafniumsilicide, i.e., HfSi_(x). The conductive material layer 32 is composedof a conductive material (metal material, specifically tungsten (W))different from that of the work function control layer 31. The workfunction control layer 31 is formed across the bottom and side portionsof the gate electrode 23 facing the channel forming region 12, and theconductive material layer 32 occupies the remaining portion of the gateelectrode 23. In the insulated gate field effect transistor of the firstembodiment, the side portion of the gate electrode 23 is in contact witha side wall film 17 composed of SiN. Around the surfaces of thesource/drain regions 13, a silicide layer (specifically, a nickelsilicide layer) 13A is formed. This is the same also in the second tofourth embodiments to be described later.

On the source/drain regions 13, the side wall film 17, and the gateelectrode 23, a first interlayer insulating layer 41 composed of siliconnitride (SiN) is deposited (formed). On the first interlayer insulatinglayer 41, a second interlayer insulating layer 42 composed of siliconoxide (SiO_(x), e.g., X=2) is deposited (formed). Furthermore, a contactplug formation opening 43A is provided in partial portions of the firstinterlayer insulating layer 41 and the second interlayer insulatinglayer 42 located above the channel forming region 12. In this contactplug formation opening 43A, a contact plug 44A that is composed oftungsten and connected to the top of the gate electrode 23 is provided.In addition, contact plug formation openings 43B are provided in partialportions of the first interlayer insulating layer 41 and the secondinterlayer insulating layer 42 located above the source/drain regions13. In these contact plug formation openings 43B, contact plugs 44B thatare composed of tungsten and connected to the silicide layer 13A of thesource/drain regions 13 are provided. Reference numeral 11 denotes asilicon semiconductor substrate.

The method for manufacturing an insulated gate field effect transistoraccording to the first embodiment will be described below, withreference to FIGS. 1A to 1I, which are schematic partial end views ofthe silicon semiconductor substrate and so on.

[Step-100]

Initially, a base 10 is prepared that includes the source/drain regions13, the channel forming region 12, the gate insulating film 30 formed onthe channel forming region 12, an insulating layer 21 that is composedof SiO₂ and covers the source/drain regions 13, and a gate electrodeformation opening 22 that is provided in a partial portion of theinsulating layer 21 above the channel forming region 12.

Specifically, after element isolation regions (not shown) are formed inthe silicon semiconductor substrate 11, a dummy gate insulating film 14is formed on the surface of the silicon semiconductor substrate 11, andthen a dummy poly-silicon layer 15 and a hard mask layer composed of SiNare sequentially formed. Subsequently, a dummy gate electrode 15′ isformed based on photolithography and dry etching. The dummy gateelectrode 15′ has a multilayer structure formed of the dummypoly-silicon layer 15 and the hard mask 16. Subsequently, after shallowion implantation of an impurity for forming an LDD structure is carriedout, a SiN layer for forming the side wall film 17 is formed on the sidesurface of the dummy gate electrode 15′, and the SiN layer is etchedback. This can form the side wall film 17 composed of SiN. Thereafter,deep ion implantation of an impurity is carried out to thereby form thesource/drain regions 13. Subsequently, a nickel layer is depositedacross the entire surface and heat treatment is carried out to therebyturn upper part of the source/drain regions 13 into a silicide. This canform the silicide layer 13A composed of a nickel silicide. Thereafter,the unreacted nickel layer is removed and heat treatment is carried outagain, to thereby stabilize the silicide layer 13A. Through this step,the source/drain regions 13 having extension regions and the silicidelayer 13A (low-resistance layer) can be obtained. The region sandwichedbetween the extension regions of the source/drain regions 13 serves asthe channel forming region 12. In this manner, the state shown in FIG.1A can be obtained.

Thereafter, the insulating layer 21 composed of SiO₂ is formed acrossthe entire surface, and then planarization treatment is carried outbased on CMP, to thereby remove a partial portion of the insulatinglayer 21 and the hard mask 16 (and further a partial portion of thedummy poly-silicon layer 15 and a partial portion of the side wall film17, depending on the case). Through this step, the state shown in FIG.1B can be obtained.

Subsequently, the exposed dummy gate electrode 15′ is removed by etchingin which a radical of fluorine or the like is used, and the dummy gateinsulating film 14 is removed by wet etching employing e.g. a dilutehydrofluoric acid. Thus, the state shown in FIG. 1C can be obtained.

Subsequently, the gate insulating film 30 is formed on the channelforming region 12 exposed through the bottom of the gate electrodeformation opening 22. In the first embodiment, initially the gateinsulating film 30 is formed on the channel forming region 12 exposedthrough the bottom of the gate electrode formation opening 22 and theside surface of the gate electrode formation opening 22. Specifically,the gate insulating film 30 that is composed of hafnium oxide and has athickness of 3.0 nm is formed across the entire surface (see FIG. 1D).This gate insulating film 30 can be formed based on e.g. CVD in which anorganic-based Hf gas is used as the source gas. Alternatively, it can beformed by forming a hafnium film based on sputtering employing a hafniumtarget and then oxidizing the hafnium film. More alternatively, it canbe formed based on ALD.

[Step-110]

After the formation of the gate insulating film 30, the gate electrode23 is formed by burying a conductive material layer in the gateelectrode formation opening 22. In the first embodiment, the gateelectrode 23 is formed of the work function control layer 31 composed ofa conductive material (metal material) and the conductive material layer32 composed of a conductive material (metal material) different fromthat of the work function control layer 31. Therefore, specifically, thework function control layer 31 that is composed of hafnium silicide(HfSi_(x)) and has a thickness of 15 nm is initially formed based onsputtering across the entire surface (specifically, on the gateinsulating film 30) (see FIG. 1E).

Thereafter, the remaining part of the gate electrode formation opening22 is filled with the conductive material layer 32, so that the gateelectrode 23 formed of the work function control layer 31 and theconductive material layer 32 is obtained. More specifically, initially abarrier layer (not shown) composed of TiN is formed based on sputteringacross the entire surface. The barrier layer with a thickness of 10 nmcan be formed based on CVD, sputtering, or ALD (in which a NH₃ gas and aTiCl₄ gas are alternately used). Thereafter, the conductive materiallayer 32 that is composed of tungsten and has a thickness of 0.2 pm isformed across the entire surface based on so-called blanket tungstenCVD. Subsequently, planarization treatment based on CMP is carried outto remove the conductive material layer 32, the barrier layer, the workfunction control layer 31, and the gate insulating film 30 over theinsulating layer 21 and the side wall film 17 (see FIG. 1F). In thismanner, the gate electrode 23 can be obtained. The gate electrode 23 isformed above the channel forming region 12 with the intermediary of thegate insulating film 30 therebetween and is formed of the work functioncontrol layer 31, the barrier layer, and the conductive material layer32.

[Step-120]

After the formation of the gate electrode 23, the insulating layer 21 isremoved (see FIG. 1G). Specifically, the insulating layer 21 can beremoved based on dry etching in which a C₄F₈ gas and an Ar gas are used.

[Step-130]

Thereafter, the first interlayer insulating layer 41 and the secondinterlayer insulating layer 42 are sequentially deposited across theentire surface. Specifically, the first interlayer insulating layer 41and the second interlayer insulating layer 42 are sequentially depositedover the gate electrode 23, the side wall film 17 and the source/drainregions 13 (more specifically, the silicide layer 13A). Subsequently,planarization treatment for the second interlayer insulating layer 42 iscarried out. As a result, the structure shown in FIG. 1H can beobtained. The first interlayer insulating layer 41 is deposited in adeposition atmosphere containing no oxygen atom. The second interlayerinsulating layer 42 is deposited in a deposition atmosphere containingoxygen atoms. More specifically, the first interlayer insulating layer41 is deposited based on CVD in which a source gas with a compositioncontaining neither oxygen atoms nor oxygen molecules is used, and thenthe second interlayer insulating layer 42 is deposited based on CVD inwhich a source gas with a composition containing oxygen atoms or oxygenmolecules is used. Examples of the film deposition conditions are shownin Tables 1 and 2.

[Table 1]

-   Condition of film deposition of first interlayer insulating layer 41    based on plasma CVD-   Source gas: SiH₄/NH₃/N₂=30 to 800 sccm/30 to 800 sccm/3000 to 5000    sccm-   Temperature: 400° C. or lower-   Pressure: 4×10² Pa to 1.3×10³ Pa

[Table 2]

-   Condition of film deposition of second interlayer insulating layer    42 based on plasma TEOS-CVD-   Source gas: TEOS gas/O₂=500 to 1000 sccm/400 to 1000 sccm-   Temperature: 400° C. or lower-   Pressure: 4×10² Pa to 1.3×10³ Pa

[Step-140]

After the deposition of the layers 41 and 42, based on photolithographyand dry etching, the contact plug formation openings 43A and 43B areformed in the first interlayer insulating layer 41 and the secondinterlayer insulating layer 42 above the gate electrode 23 and above thesource/drain regions 13. Subsequently, a second barrier layer (notshown) formed of a multilayer structure of Ti (lower layer)/TiN (upperlayer) is formed based on sputtering across the entire surface, and thena tungsten layer is formed across the entire surface based on blankettungsten CVD employing a WF₆ gas, H₂ gas, and SiH₄ gas (at a depositiontemperature of 400° C.). Subsequently, planarization treatment based onCMP is carried out, so that the contact plugs 44A and 44B can be formedin the contact plug formation openings 43A and 43B (see FIG. 1I).Thereafter, interconnects and so on (not shown) are formed on the secondinterlayer insulating layer 42 according to need, so that the insulatedgate field effect transistor of the first embodiment can be completed.

In the first embodiment, the first interlayer insulating layer 41 isdeposited in a deposition atmosphere containing no oxygen atom in[Step-130]. This feature can surely prevent the occurrence of aphenomenon of oxidation of a partial portion of the base (siliconsemiconductor substrate 11) facing the gate electrode 23, and thus cansurely avoid the occurrence of a problem of the deterioration ofcharacteristics of the insulated gate field effect transistor, such asthe lowering of the gate capacitance. Furthermore, the configuration ofthe components above the gate electrode 23 (the configuration of theinterlayer insulating layers 41 and 42) is the same as that of thecomponents above the source/drain regions 13 (the configuration of theinterlayer insulating layers 41 and 42). Therefore, in [Step-140], thecontact plug formation openings 43A and 43B can be easily formed for theprovision of the contact plugs 44A and 44B for the gate electrode 23 andthe source/drain regions 13.

Second Embodiment

The second embodiment is a modification of the first embodiment. In thesecond embodiment, the insulating layer is formed of a lower insulatinglayer 21A and an upper insulating layer 21B formed on this lowerinsulating layer 21A. The lower insulating layer 21A covers at least thesource/drain regions 13 (specifically, the source/drain regions 13 andthe side wall film 17). In the step of removing the insulating layer,the upper insulating layer 21B is removed whereas the lower insulatinglayer 21A is left. The lower insulating layer 21A is composed of thesame material as that of the first interlayer insulating layer 41,specifically, SiN. The upper insulating layer 21B is composed of thesame material as that of the second interlayer insulating layer 42,specifically, SiO_(x) (X=2). As the film deposition condition for thelower insulating layer 21A composed of SiN, the same condition as thatshown in Table 1 can be employed. Examples of the film depositioncondition for the upper insulating layer 21B composed of SiO₂ are shownin Tables 3 and 4.

[Table 3]

-   Condition of film deposition of upper insulating layer 21B based on    high-density plasma CVD-   Source gas: SiH₄/O₂/Ar (or He or H₂)=8 to 120 sccm/10 to 240 sccm/10    to 120 sccm-   Temperature: 400° C. or lower-   Pressure: 4×10² Pa to 1.3×10³ Pa

[Table 4]

-   Condition of film deposition of upper insulating layer 21B based on    O₃-TEOS-CVD-   Source gas: gas obtained by mixing a TEOS gas of 10 to 15 wt. %    (supplied at a flow rate of 500 to 1000 milligrams/minute) in a    mixture gas of O₂ and O₃ supplied at a flow rate of 5 to 10    liters/minute-   Temperature: 450° C. or lower-   Pressure: 6.7×10³ Pa to 9.3×10⁴ Pa

The method for manufacturing an insulated gate field effect transistoraccording to the second embodiment will be described below, withreference to FIGS. 2A to 2I, which are schematic partial end views ofthe silicon semiconductor substrate and so on.

[Step-200]

Initially, a base 10 is prepared that includes the source/drain regions13, the channel forming region 12, the gate insulating film 30 formed onthe channel forming region 12, the insulating layers 21A and 21Bcovering the source/drain regions 13, and the gate electrode formationopening 22 that is provided in partial portions of the insulating layers21A and 21B above the channel forming region 12.

Specifically, initially the same step as that of the former stage of[Step-100] in the first embodiment is carried out to obtain the stateshown in FIG. 1A. Subsequently, the lower insulating layer 21A that iscomposed of SiN and is to serve as a liner layer is deposited by CVDacross the entire surface based on the film deposition conditionexemplified in Table 1. Thus, the state shown in FIG. 2A can beobtained. Subsequently, the upper insulating layer 21B composed of SiO₂is deposited across the entire surface based on the film depositioncondition exemplified in Table 3 or 4, and then planarization treatmentis carried out based on CMP to thereby remove a partial portion of theupper insulating layer 21B, a partial portion of the lower insulatinglayer 21A, and the hard mask 16 (and further a partial portion of thedummy poly-silicon layer 15 and a partial portion of the side wall film17, depending on the case). Through this step, the state shown in FIG.2B can be obtained.

Subsequently, the exposed dummy gate electrode 15′ is removed by etchingin which a radical of fluorine or the like is used, and the dummy gateinsulating film 14 is removed by wet etching employing e.g. a dilutehydrofluoric acid. Thus, the state shown in FIG. 2C can be obtained.

Subsequently, similarly to [Step-100] of the first embodiment, the gateinsulating film 30 is formed on the channel forming region 12 exposedthrough the bottom of the gate electrode formation opening 22 (see FIG.2D).

[Step-210]

Thereafter, the gate electrode 23 is formed by filling the gateelectrode formation opening 22 with the work function control layer 31and the conductive material layer 32 (see FIGS. 2E and 2F). The gateelectrode 23 is formed of the work function control layer 31, a barrierlayer (not shown), and the conductive material layer 32 similarly to thefirst embodiment.

[Step-220]

Subsequently, the upper insulating layer 21B is removed similarly to[Step-120] of the first embodiment (see FIG. 2G). The lower insulatinglayer 21A is left.

[Step-230]

Thereafter, the first interlayer insulating layer 41 and the secondinterlayer insulating layer 42 are sequentially deposited across theentire surface similarly to [Step-130] of the first embodiment.Specifically, the first interlayer insulating layer 41 and the secondinterlayer insulating layer 42 are sequentially deposited over the gateelectrode 23, the side wall film 17, and the lower insulating layer 21A.Subsequently, planarization treatment for the second interlayerinsulating layer 42 is carried out. As a result, the structure shown inFIG. 2H can be obtained.

[Step-240]

Thereafter, the contact plugs 44A and 44B are formed similarly to[Step-140] of the first embodiment (see FIG. 21). Subsequently,interconnects and so on (not shown) are formed on the second interlayerinsulating layer 42 according to need, so that the insulated gate fieldeffect transistor of the second embodiment can be completed.

Also in the second embodiment, the first interlayer insulating layer 41is deposited in a deposition atmosphere containing no oxygen atom in[Step-230]. This feature can surely prevent the occurrence of aphenomenon of oxidation of a partial portion of the base (siliconsemiconductor substrate 11) facing the gate electrode 23, and thus cansurely avoid the occurrence of a problem of the deterioration ofcharacteristics of the insulated gate field effect transistor, such asthe lowering of the gate capacitance. Furthermore, the configuration ofthe components above the gate electrode 23 (the configuration of theinterlayer insulating layers 41 and 42) is substantially the same asthat of the components above the source/drain regions 13 (theconfiguration of the insulating layer 21A +the interlayer insulatinglayers 41 and 42). Therefore, in [Step-240], the contact plug formationopenings 43A and 43B can be easily formed for the provision of thecontact plugs 44A and 44B for the gate electrode 23 and the source/drainregions 13. Furthermore, in [Step-220], the upper insulating layer 21Bis removed whereas the lower insulating layer 21A is left. Therefore, inthis insulating layer removal, no damage occurs to the source/drainregions 13. Moreover, it is possible to make the lower insulating layer21A function as a liner layer, and thus stress can be applied to thechannel forming region 12. As a result, the driving ability of theinsulated gate field effect transistor can be enhanced.

Third Embodiment

The third embodiment relates to a method for manufacturing an insulatedgate field effect transistor according to the second mode of the presentinvention.

As shown in the schematic partial end view of FIG. 3B, an insulated gatefield effect transistor obtained by the method for manufacturing aninsulated gate field effect transistor according to the third embodimentalso includes (A) source/drain regions 13 and a channel forming region12, (B) a gate electrode 23 formed above the channel forming region 12,and (C) a gate insulating film 30.

In the third embodiment, a first interlayer insulating layer 41 composedof silicon nitride (SiN) is deposited (formed) on an insulating layer21, a side wall film 17, and the gate electrode 23, unlike the firstembodiment. On the first interlayer insulating layer 41, a secondinterlayer insulating layer 42 composed of silicon oxide (SiO_(x), e.g.,X=2) is deposited (formed). Furthermore, a contact plug formationopening 43A is provided in partial portions of the first interlayerinsulating layer 41 and the second interlayer insulating layer 42located above the channel forming region 12. In this contact plugformation opening 43A, a contact plug 44A that is composed of tungstenand connected to the top of the gate electrode 23 is provided. Inaddition, contact plug formation openings 43B are provided in partialportions of the insulating layer 21, the first interlayer insulatinglayer 41, and the second interlayer insulating layer 42 located abovethe source/drain regions 13. In these contact plug formation openings43B, contact plugs 44B that are composed of tungsten and connected to asilicide layer 13A of the source/drain regions 13 are provided.

The method for manufacturing an insulated gate field effect transistoraccording to the third embodiment will be described below with referenceto FIGS. 3A and 3B, which are schematic partial end views of a siliconsemiconductor substrate and so on.

[Step-300]

Initially, similarly to [Step-100] of the first embodiment, a base 10 isprepared that includes the source/drain regions 13, the channel formingregion 12, the gate insulating film 30 formed on the channel formingregion 12, the insulating layer 21 that is composed of SiO₂ and coversthe source/drain regions 13, and a gate electrode formation opening 22that is provided in a partial portion of the insulating layer 21 abovethe channel forming region 12. Specifically, the same step as [Step-100]of the first embodiment is carried out. More specifically, after thestate shown in FIG. 1A is obtained, the insulating layer 21 composed ofSiO₂ is formed across the entire surface, and then planarizationtreatment is carried out based on CMP, to thereby remove a partialportion of the insulating layer 21 and a hard mask 16 (and further apartial portion of a dummy poly-silicon layer 15 and a partial portionof the side wall film 17, depending on the case). Thus, the state shownin FIG. 1B can be obtained. Subsequently, an exposed dummy gateelectrode 15′ is removed by etching in which a radical of fluorine orthe like is used, and a dummy gate insulating film 14 is removed by wetetching employing e.g. a dilute hydrofluoric acid. Thus, the state shownin FIG. 1C can be obtained. Subsequently, the gate insulating film 30 isformed on the channel forming region 12 exposed through the gateelectrode formation opening 22 (see FIG. 1D). Thereafter, the gateelectrode 23 is formed by filling the gate electrode formation opening22 with a work function control layer 31 and a conductive material layer32 similarly to [Step-110] of the first embodiment (see FIGS. 1E and1F). The gate electrode 23 is formed of the work function control layer31, a barrier layer (not shown), and the conductive material layer 32similarly to the first embodiment.

[Step-310]

After the formation of the gate electrode 23, without the removal of theinsulating layer 21 unlike the first embodiment, a first interlayerinsulating layer 41 and a second interlayer insulating layer 42 aresequentially deposited similarly to [Step-130] of the first embodimentacross the entire surface, i.e., over the insulating layer 21, the sidewall film 17, and the gate electrode 23 (see FIG. 3A).

[Step-320]

Subsequently, the contact plugs 44A and 44B are formed in the contactplug formation openings 43A and 43B similarly to [Step-140] of the firstembodiment (see FIG. 3B). Thereafter, interconnects and so on (notshown) are formed on the second interlayer insulating layer 42 accordingto need, so that the insulated gate field effect transistor of the thirdembodiment can be completed.

In the third embodiment, the first interlayer insulating layer 41 isdeposited in a deposition atmosphere containing no oxygen atom in[Step-310]. This feature can surely prevent the occurrence of aphenomenon of oxidation of a partial portion of the base (siliconsemiconductor substrate 11) facing the gate electrode 23, and thus cansurely avoid the occurrence of a problem of the deterioration ofcharacteristics of the insulated gate field effect transistor, such asthe lowering of the gate capacitance.

Fourth Embodiment

The fourth embodiment is a modification of the third embodiment. In thefourth embodiment, the insulating layer is formed of a lower insulatinglayer 21A and an upper insulating layer 21B formed on this lowerinsulating layer 21A. The lower insulating layer 21A covers at least thesource/drain regions 13 (specifically, the source/drain regions 13 andthe side wall film 17). The lower insulating layer 21A is composed ofthe same material as that of the first interlayer insulating layer 41,specifically, SiN. The upper insulating layer 21B is composed of thesame material as that of the second interlayer insulating layer 42,specifically, SiO_(x) (X=2). As the film deposition condition for thelower insulating layer 21A composed of SiN, the same condition as thatshown in Table 1 can be employed. As the film deposition condition forthe upper insulating layer 21B composed of SiO₂, the same condition asthat shown in Table 3 or 4 can be employed.

The method for manufacturing an insulated gate field effect transistoraccording to the fourth embodiment will be described below withreference to FIGS. 4A and 4B, which are schematic partial end views ofthe silicon semiconductor substrate and so on.

[Step-400]

Initially, similarly to [Step-200] of the second embodiment, a base 10is prepared that includes the source/drain regions 13, the channelforming region 12, the gate insulating film 30 formed on the channelforming region 12, the insulating layers 21A and 21B covering thesource/drain regions 13, and the gate electrode formation opening 22that is provided in partial portions of the insulating layers 21A and21B above the channel forming region 12 (see FIGS. 2A, 2B, 2C, and 2D).Thereafter, similarly to [Step-110] of the first embodiment, the gateelectrode 23 is formed by filling the gate electrode formation opening22 with the work function control layer 31 and the conductive materiallayer 32 (see FIGS. 2E and 2F).

[Step-410]

Subsequently, the first interlayer insulating layer 41 and the secondinterlayer insulating layer 42 are sequentially deposited across theentire surface similarly to [Step-310] of the third embodiment.Specifically, the first interlayer insulating layer 41 and the secondinterlayer insulating layer 42 are sequentially deposited over the gateelectrode 23, the side wall film 17, and the upper insulating layer 21B(see FIG. 4A).

[Step-420]

Thereafter, the contact plugs 44A and 44B are formed similarly to[Step-140] of the first embodiment (see FIG. 4B). Subsequently,interconnects and so on (not shown) are formed on the second interlayerinsulating layer 42 according to need, so that the insulated gate fieldeffect transistor of the fourth embodiment can be completed.

Also in the fourth embodiment, the first interlayer insulating layer 41is deposited in a deposition atmosphere containing no oxygen atom in[Step-410]. This feature can surely prevent the occurrence of aphenomenon of oxidation of a partial portion of the base (siliconsemiconductor substrate 11) facing the gate electrode, and thus cansurely avoid the occurrence of a problem of the deterioration ofcharacteristics of the insulated gate field effect transistor, such asthe lowering of the gate capacitance.

This is the end of the description of preferred embodiments of thepresent invention. The invention however is not limited to theseembodiments. The structures and configurations of the insulated gatefield effect transistors described in the embodiments are merelyexamples and can be arbitrarily changed. In addition, the manufacturingconditions and so on for the insulated gate field effect transistorsdescribed in the embodiments are also merely examples and can bearbitrarily changed.

Although the first to fourth embodiments are applied to an n-channelinsulated gate field effect transistor, the embodiments can be appliedalso to a p-channel insulated gate field effect transistor. In thiscase, e.g. ruthenium (Ru) or TiN can be used as the material of the workfunction control layer 31. In addition, there has also been proposed amethod in which the work function value is adjusted by varying thematerial of the gate insulating film instead of varying the material ofthe gate electrode for allowing the gate electrode to have a favorablework function value (refer to e.g. Japanese Patent Laid-Open No.2006-24594). This method can also be applied to embodiments of thepresent invention.

The first interlayer insulating layer is composed of SiN in theembodiments. Alternatively, it can be formed by using SiC. In the caseof depositing the first interlayer insulating layer composed of SiCbased on CVD in which a source gas with a composition containing neitheroxygen atoms nor oxygen molecules is used, e.g. the following depositioncondition is available: the total flow rate of a (SH₃)₃SiH gas, He gas,and NH₃ gas is 700 sccm; the temperature is 400° C. or lower; and thepressure is 1.3×10² Pa to 1.3×10³ Pa.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factor in so far as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An insulated gate field effect transistorcomprising: a source, a drain, and a channel region between the sourceand the drain; a gate electrode insulated from the channel region; afirst insulating layer over the gate electrode, the insulating layercontaining no oxygen as a constituent element.
 2. The insulated gatetransistor of claim 1, further comprising a second insulating layerbetween the source and the drain and the first insulating.
 3. Theinsulated gate transistor of claim 2, wherein the second insulatinglayer comprising a lower insulating layer and an upper insulating layerand the lower insulating layer is between the upper insulating layer andthe source and the drain.
 4. The insulated gate transistor of claim 3,wherein the first insulating layer and the lower insulating layer aremade of the same material.
 5. The insulated gate transistor of claim 4,wherein the first insulating layer and the lower insulating layer aremade of SiN.
 6. The insulating gate transistor of claim 4, wherein thefirst insulating layer and the lower insulating layer are made of SiC.7. The insulated gate transistor of claim 1, wherein the firstinsulating layer is made of SiN.
 8. The insulated gate transistor ofclaim 1, wherein the first insulating layer is made of SiC.
 9. Theinsulated gate transistor of claim 1, further comprising a thirdinsulating layer on the first insulating layer, the first insulatinglayer and the third insulating layer being made of dissimilar materials.